Centrifugal casting machine

ABSTRACT

A portable, centrifugal casting machine has a drive motor and shaft that rotates a generally T-shaped rotor, the head of which is inclined relative to the stem with the trailing end of the head radially outward of the leading end thereof. A mold supporting cradle is mounted on the trailing end portion of the rotor head and a crucible, with a metal discharging outlet in the end thereof toward the cradle, is mounted for limited sliding movement along a path lengthwise of the head of the T-shaped rotor. A counterweight is mounted on the opposite end of the stem of the rotor from its head. When the motor is energized, the starting torque of the rotor drives a charge of molten metal in the crucible, by a combination of acceleration, inertia and centrifugal force, through the crucible outlet and into a mold cavity in a mold mounted on the cradle, where the metal is retained under centrifugal pressure until its sets.

Hill

[54] CIEWTWKWUGAL CASTIINC MACHWE [72] Inventor: William .11. lilill,San Diego, Calif.

[73] Assignee: international Development Corporation,

San Diego, Calif.

[22] Filed: July 141, 1969 211 App]. No.: 841,303

[51] int. Cl ..lB22d 13/116 {58] lField at Search ..164/114, 286, 287,289, 292, 164/293, 298

[56] References Cited UNITED STATES PATENTS 1,280,289 10/1918 Perry164/287 1,331,660 2/1920 Mortonson et al.. 164/287 1,767,036 6/1930Andresen et al.... ...;.164/289 2,265,043 12/1941 Moore 164/2872,749,585 6/1956 Prosen ..l64/287 X 3,371,705 3/1968 Ghiorzo et al...164/298 X FORElGN PATENTS OR APPLICATIONS Primary Examinerl SpencerOverholser Assistant Examiner-John E. Roethel Att0mey-Carl R. Brown [57]AlBS'lTCT A portable, centrifugal casting machine has a drive motor andshaft that rotates a generally T-shaped rotor, the head of which isinclined relative to the stem with the'trailing end of the head radiallyoutward of the leading end thereof. A mold supporting cradle is mountedon the trailing end portion of the rotor head and a crucible, with ametal discharging outlet in the end thereof toward the cradle, ismounted for limited sliding movement along a path lengthwise of the headof the T shaped rotor. A counterweight is mounted on the opposite end ofthe stem of the rotor from its head. When the motor is energized, thestarting torque of the rotor drives a charge of molten metal in thecrucible, by a combination of acceleration, inertia and centrifugalforce, through the crucible outlet and into a mold cavity in a moldmounted on the cradle, where the metal is retained under centrifugalpressure until its sets.

8 Claims, 6 wing Figures PATENTEDMAR 14 I972 3, 648,762

SHEET 1 BF 2 I3 FIG. I

INVENTOR. WILLIAM J, HILL BY M ATTORNEY PAIENTEDMAR 14 I972 3, 648 7'62SHEET 2 [IF 2 FIG.6

INVENTOR. WILLIAM J. HILL ATTORNEY C lENTlItllFlUG AL CASTING MACll-llllNlE BACKGROUND OF THE INVENTION In the past, centrifugal castingmachines have been devised for use by dentists, jewelers, artists andthe like, wherein a quantity of molten metal is poured into a moldcavity that is swung in a circular orbit to generate centrifugal forcethat causes the molten metal to fill the mold cavity. Most of such priorart casting mechanisms do not become effective until sufficient orbitalspeed has been attained to provide adequate centrifugal force. Thistime-delay often lessens the likelihood of effective insertion of themolten metal into the cavity, thus making it difficult to continuouslyobtain optimum castings and causing loss of the expensive molten metal.These difficulties are increased by the gradual buildup in speed of therotating mechanism, and as a result most existing machines must beaccelerated extremely rapidly and in a very short time interval that ofnecessity requires the mechanisms to be strong, power ful and bolted toa heavy base. This makes such existing mechanisms expensive,complicated, heavy, not portable, and expensive to use.

SUMMARY OF THE INVENTION It is a general objective of this invention toprovide improvements in the structural and operational characteristicsof a portable centrifugal casting machine, and more particularly toprovide such a machine that employs the inertia of a mass of moltenmetal, in combination with the starting accelerative movement of a moldmounted on a rotor, to propel the molten metal rapidly and completelyinto a mold cavity in the mold and to thereafter maintain pressure onthe metal in the mold by means of centrifugal force until the metal hascooled below its melting point to provide a fine grained, detailed andunflawed casting.

The foregoing objectives and advantages of the invention will beapparent from the following description and the accompanying drawings,wherein:

FIG. I is a perspective view of a portable centrifugal casting machineembodying the invention.

FIG. 2 is an enlarged top plan view of the machine shown in FIG. 1, withboth the cradles and the small flask being shown in section and a cornerof the base being broken away.

FIG. 3 is an end view of the head of the rotor looking in the directionof the arrows 33 of FIG. 2, the crucible, large cradle and flask beingmounted thereon.

FIG. 4 is an enlarged, sectional view taken along lines 44 of FIG. 2,the small cradle and flask being removed, and the large flask, with amold therein, being mounted in its cradle and a torch being shown in theact of melting metal in the crucible.

FIG. 5 is a fragmentary perspective view showing the head and a fragmentof the stem of the T-shaped rotor with the small flask mounted in itscradle as shown in FIG. 2, the crucible being removed.

FIG. 6 is a longitudinal, vertical, sectional view of the small cradleand flask assembly of FIG. 5, with a fragment of the rotor head beingshown.

Referring to the drawings in detail, a portable, centrifugal castingmachine A embodying the invention comprises a base It) having ahorizontal, rectangular bottom plate 11 with rubber support pads I2 andfour upright corner posts 113. An upper plate 14, shaped similarly tothe bottom plate II, is secured across the tops of the corner posts I3,and an upright motor support plate I5 extends from the lower plate II tothe upper plate I4 and is secured to both plates.

A drive motor l7, which is a well known type of controlled speed, gearreduction, electrical motor, is secured to the motor support plate ISwith its driven shaft I3 upright and extending through a hole 19provided therefor in the upper base plate I4. The motor 117 preferablyis controlled to rotate the shaft 113 at a speed of the order of 250-300r.p.m.

An enlarged head portion 20 is provided on the upper end of the motordriven shaft 18, its upper end being generally flat and normal to theaxis of rotation on the shaft. A flat, slanted T-shaped rotor 211 has asquare hole 22, see FIG. 2, in the stern thereof which is fitted onto acorrespondingly shaped projection of the shaft 118. The rotor is fixedlysecured to the shaft by a cap screw 23. The head 24 of the T'shapedrotor is inclined with its center line at an angle of approximately 60/to the center line of the rotor stem 25, the larger angle being betweenthe trailing side of the stem 25 and the trailing portion of the head24, relative to the direction of rotor rotation.

A cradle 27 for supporting a mold flask 28, herein referred to as thelarge cradle and flask, is mounted on the radially outward or trailingend portion of the rotor head 24. The cradle 27 comprises acylindrically curved plate 29 and a metal end disk 30 secured coaxiallythereto. The cradle 27 is secured to the upper surface of the rotor head24 with its axis of curvature parallel to and directly above thelongitudinal center line of the rotor head 24. The large flask 28comprises a short length of cylindrical metal tubing of a diameter tofit snugly into the cradle 27 when laid thereon as shown in FIGS. I and3.

A hole is provided in the cradle end disk 30 to receive a threaded stud311, see FIGS. 2 and 6, which stud extends endwise from the end disk 32of a smaller cradle 33, herein referred to as the small cradle. A wingnut 31a is provided for the stud 311 to anchor the small cradle 33 inposition in the large cradle as best shown in FIGS. 2 and 6. Except forits size, the mounting stud 31 and an arched cylindrical band portion 34adjacent its end disk 32, the small cradle 33 is generally similar tothe large cradle 27. A small cylindrical molding flask 26 is provided ofa size to fit snugly into the small cradle as shown in FIGS. 2, 5, and6.

Mounted for limited slidable movement along a path on the head of theT-shaped rotor 21 ahead of the large cradle 27 in the direction of rotorrotation, is a channel shaped crucible support member 35. The latter hastwo threaded studs 37 and 38 extending downwardly therefrom. These studsare fitted for guided, slidable movement in a guide slot 39, see FIG. 4,which slot extends lengthwise along the center line of the rotor head24. The slot 39 is of sufficient length to permit a crucible 4t),clamped in adjusted but slidable position on its support member 35, tomove in guide slot 39 from a position wherein the crucible is spacedinwardly from a mold 41 supported in the large cradle 27, as shown insolid lines in FIG. 4, to the position thereof shown in broken lines thesame figure. This places the discharge outlet 43 of the crucible 40closely adjacent and in line with the sprue opening of a mold 41 in thelarge flask 28 mounted in the large cradle 27. Wing nuts 42 are providedon the studs 37 and 38 for securing the crucible support member 35 infixed position on the rotor when desired, as for packing and shipping.

A pair of wing screws 43 and 44 are provided, one in each side flange ofthe crucible support member 35, for gripping therebetween the narrowerlower portion of the crucible 40 when the latter is mounted on thechannel shaped support member 35.

The crucible 40 is of suitable heat resistant material, such as iscommonly used for such purposes and for example fire clay, porcelain,graphite, or other suitable: materials, and has a curved or concaverecess 45 for melting metal and holding the molten metal prior tocasting. A hooded end portion 47 is provided on the crucible 4-0, withits inner surface converging funnellike toward a discharge outlet 43 inan end of the crucible 40.

A cylindrical counterweight 49 has an axial bore therethrough that fitsover an upright pin 50 that is secured to the end of the stem 25 of theT-shaped rotor opposite the head 24. The counterweight 49 is secured inposition by a set screw SI having a lock nut 52 thereon. The weight ofthe counter weight is between that required to balance the rotor whenset up for casting with the large cradle and flask, and that requiredwhen set up with the small cradle and flask. Exact counterbalancing isnot considered essential, since the speed of the rotor is only of theorder of 250-300 rpm, and the base is strong and rigid. However, itwould be a simple matter, well within the capabilities of a routineworker, to provide either two separate counterweights, or an adjustablecounterweight if more exact counterbalancing were desired.

For preparing a mold 41 in the large flask 28 as shown in FIGS. 1 and 4,a conventional wax pattern, not shown, but similar to the mold cavity 53in the mold 41 of FIG. 4, having a usual sprue attached thereto, is setin upright position on the large end of its sprue on a usual moldingboard, also not shown, with the large flask 28 in axially uprightposition around it. The sprue is so positioned, relative to the flask28, that the sprue will align with the discharge outlet 48 of thecrucible 40 when the parts are assembled for casting on the rotor head24 as shown in FIGS. 1 and 4. The mold 41 is prepared in a conventionalmanner using any desired or conventional molding material such asplaster of Paris, plaster and brick, dust, or other suitable materials,to invest the pattern and sprue therein. The flask 28, with the patterninvested therein, is then baked in a usual manner, gate down, inaccordance with the well known lost wax procedure, leaving the mold 41with its cavity 53 ready for casting.

The mold 41, thus prepared in the large flask 28, is placed in itscradle 27 as shown in FIGS. 1 and 4. The crucible support member 35,with the crucible 40 mounted in adjusted position thereon and secured bythe wing screws 43 and 44, is moved slidably inwardly away from the mold41. The wing nuts 42 are freed sufficiently to permit easy slidablemovement of the crucible 40 support along its path determined by thestuds 37 and 38 riding in the slot 39. A required amount of castingmetal is then placed in the crucible 40 and is heated by any suitablemeans, such as a brazing or welding torch 54, see FIG.

4, until the metal 55 is melted and has attained a required temperatureas determined by any suitable means, such as a pyrometer, not shown. Themotor 17 is then energized by means of a starting switch 57 and startsthe rotor 21 to rotate in the direction of the curved arrow in FIG. 2.The cradle and mold assembly moves with the rotor. However, the inertiaof the crucible support member 35 with the crucible 40 secured thereon,tends to restrain these two members which are cammed outwardly by theslot 39, moving outwardly along their path on the rotor head 24 definedby the slot 39 until the stud 37 contacts the trailing end of the slot39. This arrests further movement of the crucible support member 35 andthe crucible 40 relative to the rotor head 24, and these two members arethen suddenly driven to rotate with the speed of rotor 21. At thispoint, the molten metal 55 in the crucible 40, which metal is still notmoving with the rotor, carries the metal forcibly toward and out throughthe crucible outlet 48 and through the sprue opening aligned therewithand into the mold terstices of the mold cavity 53, and maintains therequired pressure on the metal during the time interval required for themolten metal to set and harden. This produces a high grade, finegrained, detailed casting without voids or shrinkage defects.

For making very small castings, the small cradle 33 is used. The cradle33 is held in position by inserting the stud 31 on the end disk 32 ofthe small cradle 33 in the hole provided therefor in the end disk 30 ofthe large cradle 27 and securing it in position by means of the wing nut31a, see FIGS. 2 and 6,

For using the casting machine A with the small flask 26, the flask 26has a mold prepared therein using a wax pattern in the manner previouslydescribed herein for the large flask. The small flask 26 with a moldthus prepared therein is then seated in the small cradle 33 as shown inFIGS. 2, 5 and 6. The

remainder of the casting procedure is the same as that describedpreviously herein for the large cradle 27 and flask 28.

The invention provides a simple, relatively inexpensive, and highlyeffective portable centrifugal casting machine, and one which producesuniform high grade castings with a minimum amount of skill required onthe part of the operator.

Having described my invention, 1 now claim.

1. A centrifugal casting machine comprising:

a rotor mounted for rotation in a plane about an upright axis; powermeans operatively connected to rotatably drive said rotor in onedirection about its axis of rotation;

a crucible for holding molten metal and having its inner surface slopingfunnellike toward a discharge outlet in an end of said crucible;

means for mounting said crucible on said rotor with said dischargeoutlet directed outwardly for permitting limited guided movement of saidcrucible relative to said rotor along a path in response to rotation ofsaid motor;

said path being fixed at an angle and intersecting a radius of said axisof rotation;

and mold support means fixedly mounted on said rotor outwardly of theouter limit of movement of said crucible along said path to support amold with its sprue opening aligned with and closely adjacent saidcrucible discharge outlet when said crucible is at its outward limit ofmovement along said path;

whereby, after the initiation of rotation of said rotor said cruciblemoves outwardly on said slot until it reaches the terminal portion ofsaid slot arresting further movement of said crucible and causing moltenmetal in said crucible to move forcibly out of said crucible and intosaid mold.

2. A casting machine as claimed in claim 1 in which, I

the path of the crucible is fixed at an angle of the order of about to aradius from the axis of rotor rotation as measured on the rearward,inward side of the intersection of the path with such radius.

3. A casting machine as claimed in claim 2 wherein,

a mold flask is provided in the form of a tube, open at both ends, andof a size and shape to conform with the cradle for stable supportthereby when placed therein.

4. A casting machine as claimed in claim 1 wherein,

the mold support means is in the form of a cradle with a member acrossits outward end to retain a mold placed therein against outwarddisplacement by centrifugal force generated by rotation of the rotor.

5. A casting machine as claimed in claim 1 wherein,

the means mounting the crucible on the rotor comprise a crucible supportmember with means for fixedly clamping the crucible thereon, saidsupport member having means for engaging an elongated guide elementprovided therefore on the rotor for guiding the crucible, fixedlyclamped in its support, along said path.

6. A casting machine as claimed in claim 5 wherein,

Y the elongated guide element on the rotor is the wall of an elongatedslot in the rotor.

7. A casting machine as claimed in claim 5 wherein,

the crucible support member is channel shaped, is mounted with itsflanges upward, and the cruciblehas a lower portion narrower than itsupper portion and of a size to fit between the flanges of the supportmember.

8. A portable, centrifugal casting machine comprising:

a base;

a shaft rotatably mounted in axially upright position on said base;

power means for rotatably driving said shaft in one said head of saidrotor being fixed before and during rota tion at an angle to said stemof approximately 60l20 with the larger angle defined by the trailingside of said stem and the trailing portion of said head of said T-shapedrotor;

means for supporting a mold having a sprue opening in an end thereof onsaid rotor head with said sprue opening directed inwardly along saidrotor head;

and a crucible mounted on said rotor head ahead of and inwardly of saidmold supporting means for limited guided movement along a path extendinglengthwise of said rotor head, the crucible having a discharge openingin the end

1. A centrifugal casting machine comprising: a rotor mounted forrotation in a plane about an upright axis; power means operativelyconnected to rotatably drive said rotor in one direction about its axisof rotation; a crucible for holding molten metal and having its innersurface sloping funnel-like toward a discharge outlet in an end of saidcrucible; means for mounting said crucible on said rotor with saiddischarge outlet directed outwardly for permitting limited guidedmovement of said crucible relative to said rotor along a path inresponse to rotation of said motor; said path being fixed at an angleand intersecting a radius of said axis of rotation; and mold supportmeans fixedly mounted on said rotor outwardly of the outer limit ofmovement of said crucible along said path to support a mold with itssprue opening aligned with and closely adjacent said crucible dischargeoutlet when said crucible is at its outward limit of movement along saidpath; whereby, after the initiation of rotation of said rotor saidcrucible moves outwardly on said slot until it reaches the terminalportion of said slot arresting further movement of said crucible andcausing molten metal in said crucible to move forcibly out of saidcrucible and into said mold.
 2. A casting machine as claimed in claim 1in which, the path of the crucible is fixed at an angle of the order ofabout 120* to a radius from the axis of rotor rotation as measured onthe rearward, inward side of the intersection of the path with suchradius.
 3. A casting machine as claimed in claim 2 wherein, a mold flaskis provided in the form of a tube, open at both ends, and of a size andshape to conform with the cradle for stable support thereby when placedtherein.
 4. A casting machine as claimed in claim 1 wherein, the moldsupport means is in the form of a cradle with a member across itsoutward end to retain a mold placed therein against outward displacementby centrifugal force generated by rotation of the rotor.
 5. A castingmachine as claimed in claim 1 wherein, the means mounting the crucibleon the rotor comprise a crucible support member with means for fixedlyclamping the crucible thereon, said support member having means forengaging an elongated guide element provided therefore on the rotor forguiding the crucible, fixedly clamped in its support, along said path.6. A casting machine as claimed in claim 5 wherein, the elongated guideelement on the rotor is the wall of an elongated slot in the rotor.
 7. Acasting machine as claimed in claim 5 wherein, the crucible supportmember is channel shaped, is mounted with its flanges upward, and thecrucible has a lower portion narrower than its upper portion and of asize to fit between the flanges of the support member.
 8. A portable,centrifugal casting machine comprising: a base; a shaft rotatablymounted in axially upright position on said base; power means forrotatably driving said shaft in one direction; a generally T-shapedrotor comprising a stem portion and a head portion with said stemportion mounted on said shaft to rotate said rotor with said shaft in aplane normal to the axis of shaft rotation; said head of said rotorbeing fixed before and during rotation at an angle to said stem ofapproximately 60*-120* with the larger angle defined by the trailingside of said stem and the trailing portion of said head of said T-shapedrotor; means for supporting a mold having a sprue opening in an endthereof on said rotor head with said sprue opening directed inwardlyalong said rotor head; and a crucible mounted on said rotor head aheadof and inwardly of said mold supporting means for limited guidedmovement along a path extending lengthwise of said rotor head, thecrucible having a discharge opening in the end thereof directedrearwardly and outwardly along said rotor head for alignment of thelatter opening with said sprue opening in a mold mounted on said moldsupporting means when said crucible is at its outward limit of movement;whereby, after the initiation of rotation of said rotor said cruciblemoves outwardly on said slot until it reaches the terminal portion ofsaid slot arresting further movement of said crucible and causing moltenmetal in said crucible to move forcibly out of said crucible and intosaid mold.